Diamond bit



March 13, 1951 Filed Aug. 24, 1946 w. s. CRAKE 2,545,195

DIAMOND BIT 2 Sheets-Sheet 1 Fig. 7

lnvzni'orz Wilfred S. C rake m his A L&ZEW

W. S. CRAKE March 13, 1951 DIAMOND BIT 2 Sheets-Sheet 2 Filed Aug. 24, 1946 l 1 LJ Fig. 8

lnvznror: Wilfred S Crakz Patented Mar. 13, 1951 Wilfred S. Crake, Houston, Tex., assignor to Shell Development Company, San Francisco, Calif., a

corporation of Delaware Application August 24, 1946, Serial No. 692,780

Claims.

This invention pertains to rotary drill bits used in drilling earth formations and relates more particularly to drill bits having a main bit, a pilot bit, and means adapted to provide an improved circulation of the drilling fluid over the drill face.

While drilling through earth formations, strata of hard material such as chert, granite or limestone are often encountered. In order to drill through these extremely hard formations, it is common practice to use a drill bit having cutting elements. such as diamonds, tungsten carbide, etc., set in the drill face. Since considerable heat is generated in drilling through hard formations, it is desirable to use a drilling bit that is effectively cooled by the drilling fluid.

Experience has shown that a solid diamond studded bit having a substantially horizontal drilling face tends to break down atthe center first, which leads to the ultimate failure of the entire bit. It is therefore an object of the present invention to provide a bit with a substantially horizontal, diamond studded, drilling face having a removable, centrally located pilot bit. When using the bit of the present invention, the outer and more expensive portion of the bit may be used with several center pilot bits before wearing out, thus saving the high cost of rebuilding the whole bit each time.

Since, in conventional bits of the pilot type, it is diflicult to balance circulation so'thatall parts of the bit are cooled evenly without bypassing some portion of the diamond facing and thus causing damage or burning of the by-passed portion, it is also an object of the present invention to provide a diamond drilling bit adapted to... distribute the necessary circulation of the drilling fluid overall of the cutting surfaces of the bit so as to provide for an effective and uniform cooling of said surfaces.

It is a particular object of this invention to provide a dual-circulation, hard-surfaced or diamond-studded drill bit wherein the main bit is lubricated and cooled by direct circulation of the. drilling fluid and the pilot bit is simultaneously lubricated and cooled by reverse circulation of the drilling fluid.

Other objects of this invention will be under stood from the following description of the present invention taken with reference to the attached drawings, wherein:

Fig. 1 is a diagrammatic view in cross-section of an embodiment of the present invention;

- Fig. 2 is a diagrammatic view partly in crosssection, taken at right angles to that of Fig. 1;

Fig. 3 is an end or face view of the bit of Fig. 1;

Fig. 4 is a diagrammatic view in cross-section of another embodiment of the present invention;

Fig. 5 is a diagrammatic view partly in crosssection, taken at right angles to that of Fig. 4;

Fig. 6 is a view of the end or face of the bit of the present invention with the pilot bit removed;

Fig. '7 is a perspective view of the main bit of the present invention showing the side reaming face;

Fig. 3 is a diagrammatic view, partly in crosssection, of another embodiment of the present invention.-

For clarity, the present drill bit will be described hereinbelow with regard to the illustrated embodiments thereof, it being understood that the present invention isv in no way re stricted to said illustrated embodiments, but has a scope defined only in the claims attached to the present specification.

Referring more in detail to the drawings:

In Fig. 1, the reference number in designates generally an embodiment of the drill bit of the present invention, which comprises a main bit or drilling portion proper H, and an auxiliary or pilot bit l2. The main bit has an upper portion comprising an internally threaded neck or shank l3 whereby the bit may be attached on an externally threaded drill pipe or string such as designated by l4. 7

The main drill bit II is substantially cylindrical and has an axial bore l5 extending inwardly therethrough from the end drilling face It. The bore I5 is adapted to receive the externally threaded shank I! of the pilot bit l2. The upper portion of the axial bore I5 is increased to form an internal recess or chamber l8 large enough to accommodate a nut l9, in screw-r threaded engagement with the shank ll of the pilot bit l2, whereby said pilot bit is anchored on the beveled shoulder 2i!v formed in the axial bore 15, said shoulder being recessed slightly in the end drilling face l6 of the main bit I I.

The main bit I I has a substantially horizontal end drilling face l6 which curves at the shoulder 22 at its periphery, to form a cylindrical sidereaming face 23. Circumscribing the recessed beveled shoulder 20 in the face of the bit II is an annular space or fluid channel 24 (as shown in Fig. 6), from which there extends radially a plurality of grooves or fluid channels 25, which widen as they radiate toward the periphery of the bit, and extend around the shoulder 22 and across the side reaming face 23 of the main bit as shown in Figures 3 and '7. These fluid channels 25 divide the entire cutting surface of the main bit into a plurality of sector-shaped cutting faces 26 which are studded with cutting elements 2'! such as, for example, diamonds. Two or more of the sector-shaped cutting faces are replaced by a relatively deep fluid channeli 28 in the face of the bit II which extends across the end face I6 widening at the shoulder 22 and side face 23 of the bit. These wide grooves provide passage for relatively large fragments of rock from the bottom of the well in an upward direction, by means of the washing action of the circulating fluid when first contacting the well bottom. 'Such fragments fall in the well, while drawing or inserting the bit and, if not removed, tend to roll under the diamondfaces and shatter the diamonds.

The pilot drill bit I2 is a substantially cylindrical body having an axial bore '29 (which 'is restricted at the end drilling. facet! of the bit).

The end drilling face 30 of thepilot bit is' hOrizontal or slightly concave, curving at the perinhery of the bit to form a shoulder 3! and an annular side-reaming face 32. ing face 32 of the pilot bit I2 is terminatedsome distance shortof the end drilling face l6,of the main bit I I. bit ta ers inwardly, forming an annular recess in the side of the bit, so that when the bit is inoperation an annular space 33 is formed between the reamed borehole 3,4'and the annular recess 35 of the ilot bit I2 (as shown in Figures 1 and 4) thus allowing the circulation of drilling fluid in said space33.

'Extending radially from the axial bore 29 in the face an of the pilot bit I2 are numerous grooves or fluid channels 36 which widen as they extend toward the peri hery of the bit and extend around the shoulder 3| of the bit and across the side-reaming face 32. These flu d channels 36 divide the cutting surface of the pilot bit into a plurality of sector-shaped cutting faces 31which are also studded with cutting elements 21. Two or more of these sector-sha ed cutting faces 31 are replaced by a relatively. deep fluid channel 33 in the face of the bit I 2 which extends across the end face .30, shoulder 3! andside face 32 of the pilot bit I2, said bit being so posi ioned. when attached to main bit I I, that fluid channel 38 .in pilot bit lies perpendicularly to the fluid channel 28 in the main bit II.

This side-ream -The upper portion of the pilot Set diametrically o posite each other in the restricted axial bore 29 of the pilot bit, are two wedge-shaped core breakers 4!! which lie on either side of the fluid channel 38. The exposed surfaces of the core breakers 4i! and concave central portion of the pilot bit 39 are also studded with cutting elements 21. As shown in Fig. 1 the axial bore 29 of the pilot bit I2 is in communication with the fluid channelZIl of the main bit, II through transverseapertures or ports 4I which pass through the shank, of the pilot bit.

During drilling operations, the circulating water or drilling fluid flows down the drill string and into. the axial bore 29 of the pilot bit I2, and is then divided into two streams. One stream is released from bore 29 through ports or apertures 4|, some of the flow entering the .deep fluid channel 28 in the end face I6 of the mainbit II, and. some of the flowentering the annular space 33,thus being, distributed to the v ri .fluid 1 1 1 6 52 be w en th m studded. sector-shaped cutting faces 26 of the main bit. A second stream of the fluid flow continues through the entire axial bore 29 and is released at the face of the pilot bit I2, some of the flow crossing the face 30' of said bit in the fluid channels 36 between the cutting segments 3? and continuing up the side-reaming face 32 to the annular space 33 where it is joined by the rest of the flowthat crossed the face of the pilot bit through the relatively deeper fluid channel 38. From the annular space 33 the first and second streams of the fluid flow across the end face It of the main bit either by means of the fluid channels, 25,between the cutting segments 2% or the relatively deeper channel 28. The flow continues up the side of the bit and the drill string.

A second embodiment of a drill bit of the present invention is shown in Figures 4 and 5 and is generally designated by the numeral 2|. It comprises a main bit II, a pilot bit 5!, the main bit having an internally threaded shank I3 which is attached on an externally threaded special section of a drill pin or collar 58, said drill pin or collar being attached to the rest of the drill string (not shown here). A slanting core tube 42, which discharges at a side aperture 43 in the side of the drill pin 58, is centeredand-anchoredin the inner bore 59 of the drill bit by means of a support or spider 44 having marginal fluid ports 45. An extension 46 of the core tube 42 extends from a point near the end face 30 of the pilot bit, through the axial bore 2Il'of said bit and out the threaded shank'I'I to such a distance that permits it to be anchored and centered'by support 44 when the bit 2| is attached to the special section of drill rod 58. 5

The main bit II of both illustrated embodiments of the invention is of similar construction. The pilot bit 5| of the second embodiment has an axial bore 29 of a diameter equal to that of the extension core tube 46, extending from a point near the end face 3!! of the pilot bit 5| to a point slightly above the face I6 of the main bit II. From this point to the end of the shank I], the diameter of the bore 29 is enlarged to" form an annular fluid passageway 43 around the extension core tube 45, communicating at one end with an internal chamber I8 and at the other end, through ports or apertures 41, with the relatively deep fluid channel 28 in the'face of bit II. Instead of a set of core breakers set in the face of the pilot bit this embodiment has a single core breaker 49 set in the axial bore 29 slightly below the face of the bit,

When this bit is being used in drilling operations, the drilling fluid is pumped down the inner bore 50 of the drill string. The fluid flows around the slanting core tube 42, through the marginal fluid ports 45 of the spider 44, into internal recess i 8, through annular passageway 48 and out apertures 41 into the deep fluid channel 28 in the main bit II and into the annular passageway 33 between the borehole wall 34 and the annular recess 35 of the pilot bit. The fluid flow entering annular space 33 is distributed in two directions One part of the flow enters the fluid channels 25 between the cutting segments 26 of the main bit, flowing across the face I5 and up the sides 23 of the main bit to the space between the drill rod and the wall of the borehole. The other part of the fluid flow leaving annular space S3 is distributed in the fluid channels 36 between the cutting segments 3'! of the pilot bit, flowing down the sides 32 and across the face 320i the pilot bit, entering the axial bore or core hole 29 in rasses the face of said bit and flowing past the core breaker 49; up. the: coretu'oe-extension M3 and the core tube 42 to be discl rargedat" the side aperture 4% into the annular space between the drill pipe and the wall of the borehole.

It will be seen that by this arrangement an especially effective and uniform distribution of the fluid to cool all cutting surfaces of the bit is achieved, the main bit using direct circulation from the drill string with the fluid flowing from the inner part of the bit to the outer edge of the bit for cooling the main bit and removing cuttings upwards through the annular space around the drill string, while the pilot bit uses reverse circulation of the fluid, from saidannular space and the outer edge of the bit inwardly to the core tube, the pilot bit being cooled by said circulation, and the core fragments broken by thev core breaker is being raised through tube 42 and ejected into the annular space at 43, being thereupon further comminuted by grinding between the string and the walls of the borehole and raised to the surface by the upward fluid flow in said annular space.

Fig. 8 shows still another embodiment of this invention. This embodiment does not have an outwardly extending pilot bit as illustrated in the other embodiments, said 'pilot bits having an undercut or tapering side forming an annular distributing channel 33 with the sides of the borehole. This embodiment utilizes a centrally located, non-cylindrical (elliptical, square, diamondor star-shaped, etc.) pilot bit 52 having a substantially horizontal or slightly concave end drilling face 53 lying in a horizontal plane with the end drilling face 54 of the main b t 56.

When this bit is being used in drilling operations, the drilling fluid flows through the annular passageway 48 and out the apertures 41 into an annular recess or groove 55 where it is distributed and then discharged through restricted channel 51, which is a continuation of annular chamber 55, to the face of the bit where the flow is divided into two streams. One stream of the fluid flow enters the fluid channels between the cutting segments of the main bit flowing across the face and up the side of the bit while the other stream is distributed in the fluid channels between the cutting segments of the pilot bit and enters the axial bore of said bit to be discharged through a core tube.

I claim as my invention:

1. A diamond drill bit comprising a substantially cylindrical main bit having an end cutting face in a plane substantially perpendicular to the axis of the bit, a pilot bit extending outwardly from the face of the main bit and having a cutting face in a plane substantially perpendicular to the axis of the bit, means detachably connecting the pilot bit to the main bit in rigid relationship therewith, an axial bore passing through the main and the pilot bit, an annu ar recess in the portion of said pilot bit extending outwardly from the face of said main bit, said recess being open to the space outside the drill bit, and transverse ports in the pilot bit in communication between said axial bore and said annular recess.

2. A diamond drill bit comprising a substantially cylindrical main bit having an end cutting face in a plane substantially perpendicular to the axis of the bit, a pilot bit extending outwardly from the face of the main bit and having a cutting face in a plane substantially perpendicular to the axis of the bit, radial channels 6. in the end cutting" faces of'said 'ma'inand pilot bits dividing said cutting faces into sector-shaped segments, means detachably connecting the pilot bit to the main bit in rigid relationship therewith, an axial bore passing through the main and the pilot bit, an annular recess in the upper portion of said pilot bit open to the radial channels in the cutting faces of the main and the pilot bit, and transverse ports in the pilot bit in communication between said axial bore and said annular recess.

3. A diamond drill bit comprising a substantially cylindrical main bit having an end cutting face in a plane substantially perpendicular to the axis of the main bit, a centrally located and substantially cylindrical pilot bit having a cutting face in a plane substantially perpendicular to the axis of the bit and extending outwardly from the face of the main bit, means detachably connecting the pilot bit to the main bit in rigid relationship therewith, radial channels in the end cutting faces of said main and pilot bits dividing said cutting faces into sector-shaped segments, said sector-shaped segments of the faces of the main and pilot bits being set with diamonds, a diametral channel across the face of the main bit, an axial bore passing through the main and the pilot bit in communication with the radial channels in the end face of the pilot bit, an annular recess in the upper portion of said pilot bit adjacent the cutting face of the main bit and open to the radial channe s in the faces of the main and the pilot bits, and transverse ports in the pilot bit opening from said axial bore to said annular recess in the pilot bit and to the diametral channel in the cutting face of the main bit.

4. A diamond drill bit comprising a substantially cylindrical main bit having an end cutting face in a plane substantially perpendicular to the axis of the main bit, a centrally located, and substantially cylindrical pilot bit having a cutting face in a plane substantially perpendicular to the axis of the bit and extending outwardly from the face of the main bit. means detachably connect ng the pi ot bit to the main bit in rigid relation hip therewith, radial channels in the end cutting faces of said main and pilot bits dividing said cutting faces into sectorshaped segments, said sector-sha ed segments of the faces of the main and pilot bits being set with diamonds, a diametral channel a ross the face of the main bit, a diametral channel across the face of the pilot bit. said channel run ning at right angles to the diametral channel in the main bit. an axial bore passing through the main and the pilot bit in communication with the radial channels and diametral channel in the face of the pilot bit, an annular recess in the upper portion of said pilot bit adjacent the cutting face of the main bit and open to the radial channels in the faces of the main and the pilot bits and transverse ports in the pilot bit opening from said axial bore to said annular recess in the pilot bit and to the diametral channel in the cutting face of the main bit.

5. A diamond drill bit comprising a substantially cylindrical main bit having an end cutting face in a plane substantially perpendicular to the ax s of the main bit, a centrally located and substantially cylindrical pilot bit having a cutting face in a plane substantially perpendicular to the axis of the bit and extending outwardly from the face of the main bit, means 7 detachably connecting the pilot bit to the main 7 bit in rigid relationship therewith, radial channels in the end cutting faces of said main and pilot bits dividing said cutting faces into sectorshaped segments, said sector-shaped segments of the faces of the main and pilot bits being set with diamonds, at least two radial grooves across the face of the main bit that are substantially deeper than said radial channels, an axial bore passing through the main and the pilot bit in communication with the radial channels in the end face of the pilot bit, an annular recess in the upper portion of said pilot bit adjacent the cutting face of the main bit and open to the radial channels in the faces of the main and the pilot bits, and transverse ports in the pilot bit opening-from said axial bore to said annular recess in the pilot bit and to the radial grooves in the cutting face of the main bit.

WILFRED S. CRAKE.

8 REFERENCES CITED UNITED STATES PATENTS Number Name Date 923,514 Hardsocg June 1, 1909 1,096,134 Sims May 12, 1914 1,785,405 Candee et a1. Dec. 16, 1930 2,053,801 Mitchell Sept. 8, 1936 2,256,092 Koebel et a1. Sept. 16, 1941 2,264,440 Havlick Dec. 2, 1941 2,282,596 Wise et a1. May 13, 1942 2,371,489 Williams Mar. 13, 1945 2,381,415 Williams Aug. 7, 1945 FOREIGN PATENTS Number Country Date 337,785 France Mar, 1, 1904 

